Abrasive articles have long been known in the art, and have been used to abrade, finish, or polish a variety of surfaces. One type of abrasive article is a coated abrasive article, which comprises abrasive grains adhered to a backing. Paper and cloth have long been used as backing materials for coated abrasive articles. Abrasive grains may also be adhered to other types of backings, including inflexible backings.
Coarse-grade abrasive grains are incorporated into abrasive articles for rough high stock removal of material from a workpiece. On the other end of the spectrum, extremely fine abrasive grains, sometimes referred to as microabrasive grains, are incorporated into abrasive articles to achieve a close tolerance finish or polish. Coated abrasive articles containing microabrasive grains are used, for example, for magnetic head finishing; polishing or burnishing floppy disks; creating high-gloss finishes on acrylic surfaces; and providing a final finish to stainless steel or brass.
Whether the coated abrasive article utilizes microabrasive grains, coarse-grade abrasive grains, or other types of abrasive grains, it has long been recognized that the abrading surface of the article can be clogged or gummed by material worn from the workpiece. One way this problem has been addressed is by applying the abrasive grains on a backing in a dot pattern or matrix pattern. See, for example, U.S. Pat. Nos. 3,246,430 (Hurst); 794,495 (Gorton); 1,657,784 (Bergstrom); 4,317,660 (Kramis et al.). When abrasive grains are disposed in a pattern, pathways exist for abraded material to be removed.
Coated abrasive articles having abrasive grains arranged in a dot pattern have been prepared by applying an adhesive to a backing in a desired dot pattern. The backing is then flooded with abrasive grains that adhere to the dots of adhesive. Alternatively, the abrasive grains can be applied in a desired pattern to a continuous adhesive layer.
Other types of abrasive tools have been made by setting abrasive granules, such as diamonds, into a desired pattern by hand. It does not appear that hand setting of large abrasive granules, such as diamonds, has been employed in a commercially available, flexible coated abrasive article.
Abrasive grains, even when tightly graded, vary in size, and are typically of an irregular shape. However, the inability to regulate the number and position of these abrasive grains sometimes causes problems, such as uneven cutting rates, and scratches of unacceptable dimensions. These problems are accentuated in microabrasive applications.
U.S. Pat. No. 4,930,266 (Calhoun et al.) discloses an abrasive article able to produce fine finishes at high cutting rates. Calhoun et al. disclose a printing process to position individual abrasive grains or agglomerates in a regular, predetermined pattern. Thus, the article described in Calhoun et al. is able to produce a relatively predictable, consistent, and repeatable finish.
There is a need for an abrasive article that has abrasive members having a precise, lateral spacing and a consistent and desired orientation relative to the backing. The Calhoun et al. printing process places abrasive grains and agglomerates in a random orientation on the abrasive backing.